1. Field of the Invention
The invention relates to wireless networks and, more particularly, to a method and apparatus for providing mobile inter-mesh communication points in a multi-level wireless mesh network.
2. Description of the Related Art
Data communication networks may include various, hubs, switches, routers, and other network devices, interconnected and configured to handle data as it passes through the network. These devices will be referred to herein as “network elements.” Data is communicated through the data communication network by passing data packets (or cells, frames, or segments) between the network elements by utilizing one or more communication links. A particular packet may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network. Links may be formed over physical structures, such as copper cables and optical fibers, or over wireless links formed using infra-red transmissions or transmissions in a portion of the electromagnetic spectrum.
Network elements can be used to form a wireless mesh network. One characteristic of a mesh network is that in a mesh network there are generally multiple paths through the network that a given user may employ to reach the access point. By allowing traffic to hop from user to user, instead of requiring wireless transmission to take place directly between the user and an access point, it is possible to provide enhanced signal quality to users, especially where the signal may be impeded due to obstacles and other naturally occurring signal impediments. In a mesh network, an access point serves as a connection between the mesh network and a higher bandwidth communication resource, and relay points in the mesh network handle traffic for themselves and for neighbouring users.
One example of a mesh network is an 802.11b access mesh. If a set of users in close geographical proximity are equipped with 802.11b cards, they can communicate with other users in a series of hops until reaching an access point of the mesh network. Typically the access point is connected to a fixed network using a point-to-point link such as an optical fibre, copper loop, or via another wireless transmission. Due to latency and system complexity the number of wireless router hops is typically kept to some maximum, for example six. This limits the area of coverage of a wireless mesh network to a “cluster” or neighbourhood community, the clusters being connected to the fixed network via the access points. Additional access points may be added to reduce the number of hops between users and access points, and hence to reduce latency and an amount of occupied bandwidth on the mesh.
An example of a conventional arrangement of wireless meshes is shown in FIG. 1. Another example of a wireless mesh network is given in US Patent application publication no. US 2002/0159409 A1, the content of which is hereby incorporated herein by reference. In the example illustrated in FIG. 1, a number of different mesh networks 10 are shown, each of which may be on the scale of a neighbourhood. Each mesh network 10 has a number of relay points 1 connected together and configured to handle traffic on the mesh. For example, each household in a neighbourhood may be a relay point in the mesh network, the relay points being interconnected using 802.11b wireless links 14. It is noted that there may be further 802.11b devices communicating with a given relay point's location, such as in a Local Area Network (LAN) or Personal Area Network (PAN). These devices use the same technology as the relay point, can communicate with other relay points, and are considered part of the same mesh network.
In the example illustrated in FIG. 1, each mesh network 10 has an access point 16 connected to a higher bandwidth communication resource such as a Wide Area Network (WAN) base station 18 via a first tier backhaul link 20. The backhaul links 20 may be formed using a conventional point-to-point or point-to-multipoint wireless or wireline technology. In either instance, there is a single path from each access point 16 to the WAN base station 18. In the example shown in FIG. 1, the WAN base station 18 is connected via second tier wired or wireless backhaul link(s) 22 to further networking equipment, such as a central office 24. Due to the large number of first tier backhaul links 20, the full capacity of the first tier backhaul links may not be utilized. Indeed, depending on network architecture, the first tier backhaul links may be required to carry as little as 5% of their available capacity to prevent the call blocking ratio on the secondary backhaul link 22 from becoming onerous. This underutilization of the first tier backhaul links represents an over-provisioning in the first tier backhaul network which is necessary, given the limited geographical range of the mesh networks 10 being served by the first tier backhaul links 20.
Access points must be deployed and must be maintained after deployment. Installation of an access point requires the network operator to secure appropriate rights to the real estate where the access point is to be deployed, and requires the access point to be connected to a source of electrical power. Maintenance includes routine servicing, as well as servicing of the access point in the event of a failure. Larger numbers of access points increase both initial deployment costs and ongoing operation costs. These costs present potential impediments to proliferation of wireless mesh networks.